# Question #6a04a

This is a well known pattern: $\left(x y - a b\right) \left(x y + a b\right) = {\left(x y\right)}^{2} - {\left(a b\right)}^{2}$
Because of the properties of exponents ${\left(x y\right)}^{2} - {\left(a b\right)}^{2} = {x}^{2} {y}^{2} - {a}^{2} {b}^{2}$
Therefore, the final answer is: $\left(x y - a b\right) \left(x y + a b\right) = {x}^{2} {y}^{2} - {a}^{2} {b}^{2}$